The shape of our solar system's orbits.

What's the shape of the planets orbiting the sun in our solar system according to this websitehttp://www.chacha.com/question/what-is-the-shape-of-orbit-of-planets
they are elliptical. But in a documentary (maybe history channel's "The Universe", but I'm not sure) I heard that our solar system is one of the few known systems with round orbits.Majority of the others have elliptical. So what's the truth?

What's the shape of the planets orbiting the sun in our solar system according to this websitehttp://www.chacha.com/question/what-is-the-shape-of-orbit-of-planets
they are elliptical. But in a documentary (maybe history channel's "The Universe", but I'm not sure) I heard that our solar system is one of the few known systems with round orbits.Majority of the others have elliptical. So what's the truth?

A quick calculation shows that the average eccentricity of our SS's 8 major planets is ~0.0606
while the average of the 345 extrasolar planets with known eccentricities is ~0.2181
or about 3.5 times more eccentric.

But does that tell us about the extrasolar planet orbits or about the extrasolar planet detection mechanism?

No doubt that's a factor.

But there are about 55 or so planets whose eccentricity is listed as unknown. I did not include those ones. Since 'unknown' is explicitly listed, it was a reasonable assumption that the listed values are trustworthy enough for a rough calculation.

A quick calculation shows that the average eccentricity of our SS's 8 major planets is ~0.0606
while the average of the 345 extrasolar planets with known eccentricities is ~0.2181
or about 3.5 times more eccentric.

The average does not give the complete picture. If you run the data through a frequency analysis, about 1/3 of the observed eccentricities are less than 0.05 (approximately the solar system average) and around 2/3 are less than 0.2.

The above doesn't take the distance of an exoplanet from its star into account and its conceivable that planets within different AU ranges could show different means. Furthermore, and this is purely conjecture on my part, it is possible that exoplanets with larger eccentricities are the larger gas giants and thus easier to observe. The data may be inherently biased by our current observational limitations.

In any case, if 30% of the observed exoplanets match the solar system average, then the solar system cannot be considered to be that unique.

The average does not give the complete picture. If you run the data through a frequency analysis, about 1/3 of the observed eccentricities are less than 0.05 (approximately the solar system average) and around 2/3 are less than 0.2.

The above doesn't take the distance of an exoplanet from its star into account and its conceivable that planets within different AU ranges could show different means. Furthermore, and this is purely conjecture on my part, it is possible that exoplanets with larger eccentricities are the larger gas giants and thus easier to observe. The data may be inherently biased by our current observational limitations.

In any case, if 30% of the observed exoplanets match the solar system average, then the solar system cannot be considered to be that unique.

That's why I said "quick calculation" rather than "exhaustive calculation".

But you're right. The OP's post states "... our solar system is one of the few known systems with round orbits. Majority of the others have elliptical."

...which is clearly not what the data is showing when analyzed more carefully than a simple average.

In any case, if 30% of the observed exoplanets match the solar system average, then the solar system cannot be considered to be that unique.

It could be. If the you have 30% of the exoplanets match the solar system average, and the eccentricities are random, then the odds of have eight planets all with more or less round orbits is quite low. Apparently there is a resonance between Jupiter and Saturn that keeps the rest of the planets in line.

I've heard this discussed in terms of the anthropic principle. Why are solar system orbits rather round? Because if they weren't we wouldn't be seeing them.

It could be. If the you have 30% of the exoplanets match the solar system average, and the eccentricities are random, then the odds of have eight planets all with more or less round orbits is quite low.

True but only if the eccentricity of each exoplanet is determined independently.

Apparently there is a resonance between Jupiter and Saturn that keeps the rest of the planets in line.

This argument could actually extend to other systems. Current observations very likely detect the largest object(s) within an extrasolar system. And if 30% of those have low eccentricities, then its possible that other smaller objects within these systems will also be forced into circular orbits.

All satalites move about primaries that are moving also. If the positions of the two bodies were ploted over time These plots would resemble a spiral. Sorry I live in a universe that has at least four dimentions not two.

Tom is thinking that, from an external reference point, the elliptical orbit coupled with proper motion of the system results in a helical path, which he is then mistakenly calling spiral.

Tom, the path a planet follows is entirely dependent on the observer's frame of reference. You have chosen the FoR that is from a body in relative motion along the axis of the solar system in which the planet is orbiting. By saying all orbits are [helical] you've mistakenly assumed a FoR reference that is somehow more valid than any other.

Hard to tell what he's thinking. He might be including some very small braking effects, such as the emission of gravitational radiation (which always happens), or Poynting-Robertson drag (which is a larger effect in most circumstances but requires the orbiting body to be warmed by the body it's orbiting so that it emits radiation. Or he might just be being silly - who knows?